1. Field of the Invention
This invention is an alkoxy-functional room temperature vulcanizing (RTV) composition, curable in the presence of moisture, comprising polymers containing on average at least 1.2 alkoxysilyl chain terminations per molecule, a tetraalkoxytitanium compound, a filler, and an alkoxysilane. The addition of these components in amounts to satisfy defined molar ratios provide fast curing alkoxy-functional RTV compositions.
2. Background Information
Polyorganosiloxane compositions which cure to elastomeric materials at room temperature are well known. Such compositions can be obtained by mixing polydiorganosiloxanes having reactive groups, such as silanol groups, with silane crosslinking agents, for example, alkoxysilanes, acetoxysilanes, oximosilanes, or aminosilanes. Compositions comprising these ingredients can then be cured by exposure to atmospheric moisture at room temperature.
Moisture curable compositions are well known for their use as sealants. In certain applications, it is necessary to use a sealant which can cure quickly. Sealant compositions which cure quickly include silicone sealant compositions which evolve acetic acid, ketoximes, or amines as by-products during cure. These by-products have unpleasant odors and may corrode sensitive metals or plastics. The use of other compositions which would not have these properties would therefore be beneficial. One potential alternative to these compositions is an alkoxy-functional RTV composition which would liberate alcohol during cure. However, alkoxy-functional RTV compositions containing tetraalkoxytitanium compounds such as tetraisopropoxytitanium and tetra-n-butoxytitanium, are known to be slow to cure, seldom having tack-free-times (TFT) of less than 60 minutes. Therefore, these compositions are not suitable for applications requiring fast cure.
The present inventors have unexpectedly determined that fast curing alkoxy-functional RTV compositions may be prepared, however, when certain tetraalkoxytitanium compounds, for example tetra-tertiary-alkoxytitanium compounds, are added in amounts to satisfy defined molar ratios.
The objective of this invention is to prepare a fast curing alkoxy-functional RTV composition.